For those who choose to drink alcohol, the healthiest level of consumption is typically defined as up to a drink per day for women, or up to two per day for men. “Low-risk” drinking, meanwhile, is defined for women as no more than three drinks in a single day and no more than seven per week; for men, it’s four in a day and 14 per week. People who exceed these benchmarks are considered at risk for alcohol use disorder, as well as health conditions such as cancer and cognitive decline.

As clear as these definitions are on paper, however, identifying problem drinking can be more challenging in real life. Tolerance levels, behavior and personal definitions of acceptability can be highly variable, sometimes making it difficult to suss out who has troublesome drinking habits. But a new study, published this week in Alcohol & Alcoholism, identified five distinct subgroups of problem drinkers, potentially making it easier to zero in on unhealthy behavior and tailor treatments.

“Alcohol use disorder is not really a one-size-fits all diagnosis,” says study co-author Ashley Linden-Carmichael, an assistant research professor of biobehavioral health at the Pennsylvania State University. “This [approach] allows us to be more fine-tuned in detection and early screening and early prevention.”

Dr. Olivera Bogunovic, medical director of ambulatory services in the division of substance use disorders at Massachusetts’ McLean Hospital (who was not involved in the new research), agrees with that premise. “The best possible treatment for any illness in psychiatry is when it’s customized to a patient’s needs,” Bogunovic says. “The more we have some classifications, it can help clinicians gear the treatment a little bit and make it more personalized.”

The paper was based on data from about 5,400 current drinkers between the ages of 18 and 64. Each of these individuals reported at least two of 11 symptoms of a past-year alcohol use disorder — enough to qualify for a clinical diagnosis. These symptoms included at times drinking more or longer than intended, struggling to cut back, experiencing physical side effects or withdrawal symptoms from alcohol, finding that drinking interfered with personal or professional life and continuing to drink despite health or personal problems.

Across the board, drinkers tended to report having consumed more alcohol, or drinking for a longer period of time, than intended. But from there, trends emerged that allowed the researchers to sort individuals into five classes of drinkers.

The most common classification, “adverse effects only,” applied to the 34% of people in the study who said they had experienced hangovers or withdrawal symptoms related to excessive drinking, but few other problems. This classification was most prevalent among young adults.

Next in prevalence, at 25%, were those at risk of “alcohol-induced injury,” through behaviors such as driving, swimming or engaging in unsafe sex while under the influence. Surprisingly, Linden-Carmichael says, this trait was most common among older adults, peaking around age 58. “I thought that was so interesting that I double- and triple-checked my data,” Linden-Carmichael says. She speculates that young adults may be more likely to use ride-sharing services after drinking, rather than driving themselves, or may be less likely to view activities they engage in while drunk as dangerous.

After that came the “highly problematic, low perceived life interference” group, making up about 21% of the sample. These individuals reported many symptoms of problem drinking, except those that dealt with adverse effects on home life, job or academic performance. Young adults made up a disproportionately high percentage of this class as well — perhaps because for many young people, especially college students, drinking is a major part of their social lives, rather than an impediment. “They have a lot of freedom. They can do whatever they want,” Linden-Carmichael says. “My guess is they think it doesn’t interfere with their life, but it does.”

Thirteen percent of respondents fell into the “difficulty cutting back” class, or those who had a low prevalence of most symptoms but who struggled to reduce their alcohol consumption. Adults older than 53 were most likely to fall into this group. “If someone is in their 60s, it’s possible that they’ve been experiencing symptoms of a use disorder for a long time,” Linden-Carmichael says. “They’re at this precipice of, ‘How do I cut back?’ and realizing that they’re struggling to cut back.”

Finally, the least common but most severe group was considered “highly problematic.” These individuals, making up 7% of the study group, had a high probability of reporting all symptoms associated with alcohol use disorder, including negative effects on their lives and health. Although prevalence was relatively low and fairly consistent across age groups, it peaked at age 48.

Bogunovic says the paper’s subtypes are “in line with what we see clinically” and “rather comprehensive,” adding that she could see using them for future patient treatments.

That may be surprising to people outside the medical field, who tend to associate alcohol use disorder only with the most severe classification. Linden-Carmichael says the most important takeaway of the study is that the definition doesn’t, and shouldn’t, stop there.

“A lot of people think of someone with an alcohol use disorder as someone who is in the highly problematic class, and is meeting every single one of these symptoms,” Linden-Carmichael says. “But that’s not the case. Alcohol use disorder doesn’t just look like class five. It looks like all of these.”